He said, essentially, that M is convinced he is going to die broke and forgotten. Sadly, he seems determined to make that happen.
This is romantic, and probably hot air to an extent. I'd imagine it stems from what he understands and/or feels about the romantic poets. Particularly Keats, who died presuming all was lost, that his work was in vain, and that he would be forgotten - 'here lies one whose name was writ in water'.
Morrissey might secretly be convinced he faces a similar fatalistic outcome, but it's just not realistic in his case. The degree of success however, is a different thing. He may be convinced that he will pass at a time when he is not enjoying the level of success and recognition he feels he deserves.
He is just very predisposed to fatalism, and amongst other things he should maybe try giving French Poetic Realist cinema a rest for a while, to see if he feels any better about things!
As for money, unless he is trying to burn through it intentionally, or doing very frivolous things, it's not likely he could spend it all. What does he need it all for anyway, and what is he doing with it all? Apart from being decadent? Is it just one of the main ways he can quantify or justify his importance or deserving merit? I think money for him is some form of self-validation, to the extent that his quest for money has become increasingly more intense (and the equal and opposite fear of losing it equates to some sort of deep failure of the self)
It's possible he is living beyond his means, as Wilde did, but I just can't see him finding himself in dire straits like Oscar did (I don't mean the band!)
There are a few other things that are probably on his mind beyond career and material success though. Possibly no life partner.... No children... No other significant close family remaining... Friends dwindling... Who will take on custody and stewardship of his catalogue and legacy? Who is going to execute his will and deal with his estate? Lawyers? Will there be a funeral.... If there is one, who will be invited (if anyone).... and how many of those will attend.
Will all or most of his money go to PETA? The speculation is endless.